Fuse indicator



Aug. 4, 1942. 3. LA M 2,292,005

' FUSE INDICATOR Filed March '7, 1941 .O @4 15. '3 4 q INVENTOR.

M Z W 0f; ,orro/zws Patented Aug. 4, 1942 UNITED STATES PATENT OFFICE FUSE INDICATOR Frank G. La Mar, Tucson, Ariz.

Application March 7, 1941, Serial No. 382,149

4 Claims.

This invention relates to electrical fuses, especially to electrical fuses of the cartridge type, and

. more particularly to an indicator for such fuses which acts to give information as to the integrity of the fusible element of a fuse.

It is well understood by those skilled in the electrical art that safety requires that all circuits which carry, or are capable of carrying, an appreciable amount of current shall have inserted therein safety devices to prevent an excessive flow of current under abnormal conditions.

A common safety device is the well known fuse made of a strip of metal which will melt upon the flow therethrough of an undesirably heavy current.

Fuses are made of many forms, amongst which the cartridge fuse is a common form. The cartridge fuse may be either of the ferrule type or of the knife blade type. In either case, it is desirable to provide a convenient and simple form of means adapted to indicate the fact that the fusible metal has melted without making it necessary to first remove the fuse from its position and to disassemble the fuse.

Heretofore it has been customary to attach indicators to fuses by means such that a mere strong pull would be sufficient to detach the indicator from its associated fuse.

It has been found, in actual practice, that when indicators are applied to the fuses used in places where there is excessive shaking or vibration, as on battleships, that the indicator must be most securely attached to its associated fuse.

A principal object of this invention is the production of a device of the type described which will be especially adapted for use in places where there is excessive vibration, such as battleships.

A further object of the invention is the production of a device of the type specified in which there is provided means for attaching an indicator to its associated fuse which will hold the indicator as securely as circuit conductor terminals are secured to the fuse.

A further object of the invention is the production of a device of the type specified in which all of the current carrying parts of the indicator, except the connecting clips, are enclosed in an insulating case, and the connecting clips are so disposed that substantially no part of the bare clip extends sideways beyond the center line of the indicator toward the next adjacent fuse.

A further object of the invention is the production of a device of the type specified in which the indicator will be a visual one of the lamp type enclosed in an insulating case provided with a sight orifice and provided with novel means for supporting the lamp, its associated resistance, and with novel means for closing the case.

Other objects and advantages will appear as the description of the particular physical embodiments selected to illustrate the invention progresses and the novel features will be particularly pointed out in the appended claims.

In describing the invention in detail and the particular physical embodiment selected to illustrate the invention, reference will be had to the accompanying drawing, and the several views thereon, wherein like characters of reference designate corresponding parts, and in which:

Figure 1 is a view partly in elevation and partly in section of a device embodying applicants invention; Fig. 2 is a top plan View of the device as shown by Fig. 1; Fig. 3 is an end view of the device as shown by Fig. 1; Fig. 4 is a bottom view of the indicator as shown in Fig. 1; Fig. 5 is a view of a modified form of indicator; Fig. 6 is a detail view of a clip used with the indicator of Fig. 4; Fig. 7 is a detail view showing cooperation between the clip and a casing of an indicator.

In the figures, numeral I designates a fuse. This fuse is assumed to be of the usual or ordinary type having a body 2 of insulating material and metallic ferrules as 3 and 4 at each end and within the casing, connecting the ferrules 3 and 4, is assumed to be the usual fusible element.

The fuse I is held in the usual and ordinary fuse clips 5 and 6. These fuse clips have provided integrally therewith the metallic connecting means as 1, through which passes the usual headed screw 8 screw threaded in the extension I and used for attaching the circuit conductor terminals as 9.

All of the parts hereinbefore described are old and well known and usual in the art.

[0 designates a fuse integrity indicator considered as a whole. This fuse integrity indicator may assume several general forms but is preferably in the form of a casing and this casing is preferably in the form of a hollow tube H and made of insulating material, preferably hard fibre or so-called, bone fibre.

The indicating means used in the indicator is preferably a lamp I2 and preferably of the discharge type such as the well known neon lamps, that is, a lamp having two spaced terminals or electrodes therein which are filled with neon or neon with an admixture of some of the other rare gases such as helium and argon. The lamp [2 is positioned within the casing I I and it is preferred to form an orifice I3 in the casing which orifice will serve as a view slot to observe whether or not the lamp I2 is lighted.

The lamp I2 is connected, in effect, in shunt to the fuse I so that when the fuse I is blown or melted, the lamp I2 will light and indicate the non-integrity of the fuse.

In order to connect the lamp I2 in shunt to the fuse I, applicant employs conducting clips or terminals as I4 and I5, one at each end of the casing II. These clips or terminals I4 and I5 may be in any suitable or appropriate form but are preferably bifurcated so as to receive the headed screw 6 and to be pressed down and held down in place securely and immovably by screwing down the headed screw 8. Each of the clips I4 extends at a right angle to the longitudinal axis of the casing II and substantially all on one side of that longitudinal axis so that the danger of the current carrying parts I4 and I5 coming in contact with an adjacent fuse structure is obviated. In the form as shown by Figs. 1, 2, 3 and 4, the clips have one bend therein. This bend is a complete 180 or return bend and provides a portion I6 which is extended within the casin II. The clip may be held securely to the casing II by a construction to be hereinafter more fully described without the use of a rivet but it is preferred to attach each clip to the casing II by a rivet as I! passing through the portion or tongue of the clip extending into the casing and through the adjacent wall of the casing, however, it will be seen by reference to Fig. 7 that the return bend may be made so that the casing wall may be squeezed quite tightly between the clip and its return bend and it may also be seen by Fig. 6 that the tongue or portion extending within the casing may be serrated so as to provide means which will dig into the material of the casing and serve to prevent the withdrawal of the tongue therefrom, as the serrations are made so that the teeth point toward the near end of the casing.

In order to complete the connections to the lamp I2 the conductor I8 is connected to the clip I5 in any suitable or appropriate manner as by soldering at the point I9 and then the clip is put into place as shown in Fig. 1 and the rivet 20 put in place, there being interposed between the lamp I2 and the conductor I8 the usual and customary resistance 2I of the grid leak type of the order of say 25,000 to 50,000 ohms, one end of which by the conductor 22 connects with one electrode 23 of the lamp I2. The other electrode 24 of the lamp I2 is connected by a conductor 25. This conductor 25 is of such length that the tongue I6 or portion of clip I4 which extends within the casing may be soldered to the conductor 25 before the clip is put in position as shown in Fig. 1. After it is put in position as shown in Fig. 1 the clip may be riveted, as by the rivet II.

In order to suitably support the lamp I2, applicant provides the lamp support 26 which may be made of any suitable or appropriate material but is preferably made of thin fibre and is in the form of a strip with a right angle bend at one end pro vided with an orifice 21 to receive the tip of the lamp I2 and at the other end is positioned under the tongue I6 of the clip I4 so as to be thereby held in place.

After clips I4 and I5 have been but in place the ends of the casing are closed by plugs as 28 and 29. These plugs may be of suitable or appropriate material but it is preferred to make them of a fairly soft rubber so that they may be pushed into place and by their resiliency hold themselves in place. These plugs 28 and 29 are further initially formed with a flattened portion at 30 where they bear against the tongue I6 of a clip so that even if a clip is not riveted, as by the rivet IT, to the casing due to the plug and its flattened portion it will be held quite securely in place aided by the serrations as shown by Fig. 6 and by the fact that the wall of the casing II may be held quite closely between the clip and the return bend portion I6.

Although the form of indicator and clip as shown by Fig. 4 provides a device in which there is substantially no current carrying parts on one side of the longitudinal axis of the casing, nevertheless, the form shown in Fig. 5 provides a device in which there is absolutely no current carrying parts exposed outside of the casing on one side of the longitudinal axis of the casing, because the clips 30 and 3| of Fig. 5 have two bends therein, one, as shown in Fig. 5 being a vertical bend 32 and the other, 33, being exactly like the return bend of Figs. 1 to 4, inclusive.

In the form of indicator shown by Fig. 1, the clip as 3I emerges from the casing from what might be called the side rather than from the bottom, as shown by Fig. 4, so that all of the uncovered current carrying parts are on one side of the casing and that side the one which is toward the fuse to which the indicator is to be attached so that absolutely no current carrying parts of the indicator are in position to be contacted by an adjacent fuse structure.

Although I have particularly described a particular embodiment of my invention and explained the principle, construction and mode of operation thereof, nevertheless, I desire to have it understood that the form selected is merely illustrative but does not exhaust the possible physical embodiments of the idea of means underlying my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An indicator for fuses, including a casing, a lamp within the casing, conducting clips, one

positioned at each end of the casing, each conducting clip including a portion projecting within the casing and a portion without the casing extending in a direction substantially at a right angle to the longitudinal axis of the casing and substantially free from any portion extending in the opposite direction on the other side of the longitudinal axis, means for electrically connecting each conductor clip to the lamp, insulating plugs, each formed with a flat face, one driven into each end of the casing with the fiat face abutting the portion of the adjacent clip extending into the casing, said conducting clips adapted to make contact with the conductor terminals of a fuse clip.

2. An indicator for fuses, including a casing, a lamp within the casing, conducting clips, one positioned at each end of the casing, each conducting clip including a portion projecting within the casing and a portion without the casing extending in a direction substantially at a right angle to the longitudinal axis of the casing and substantially free from any portion extending in the opposite direction on the other side of the longitudinal axis, means for attaching each conducting clip to the casing, means for electrically connecting each conductor clip to the lamp, insulating plugs, each formed with a fiat face, one driven into each end of the casing with the flat face abutting the portion of the adjacent clip extending into the casing, said conducting clips adapted to make contact with the conductor terminals of a fuse clip.

3. An indicator for a fuse including a casing, a lamp Within the casing, conducting clips, one positioned at each end of the casing, means for electrically connecting each conductor clip to said lamp, each conductor clip formed with a tongue projecting into said casing, rivets, one passing through each tongue of the casing and securing the tongues to the casing, insulating resilient plugs, each formed with a fiat face, one driven into each end of the casing with the fiat face abutting the said tongue, and each conductor clip formed with means for attachment to the terminal connectors of a fuse clip.

4. An indicator for fuses, including a casing, a lamp within the casing, conducting clips, one

positioned at each end of the casing, each conducting clip including a return bend portion projecting within the casing and embracing the wall of the casing and each conductor clip including a portion Without the casing extending in a direction substantially at a right angle to the longitudinal axis of the casing and free from any portion extending in the opposite direction on the other side of the longitudinal axis of the casing, means for electrically connecting each conductor clip to the lamp, insulating plugs each formed with a flat face, one driven into each end of the casing with the flat face abutting the portion of the adjacent clip extending into the casing, said conducting clips adapted to make contact with the conductor terminals of a fuse clip.

FRANK C. LA MAR. 

